Experimental techniques which facilitate precise observations on distribution and development of Brugia malayi in regional lymphatics of cats will be used to continue studies on the interaction of this parasite of man and secondary infection with microorganisms. The level of anthelmintic therapy required to effectively treat each stage of the parasite will be determined. Radiologic techniques will be used to evaluate changes in the parasitized lymph node or vessel following secondary infection with streptococci or with a cutaneo-lymphatic fungus, Sporothrix schenckii. Changes in gross appearance of the affected limb following treatment with an anthelmintic and following infection with micro-organisms will be documented by photography. At necropsy, the location of living and dead worms will be correlated with dilated lymphatic vessels and with areas of edema and necrosis seen during the infection. It is anticipated that these studies will form a solid basis for future chronic studies on the effect which living or dead lymphatic-dwelling worms have on colonization of microorganisms and on the ultimate structure and function of regional lymphatics following treatment with anthelmintics. Results from these studies should be of value in future filariasis research projects and in management of individual patients suffering from lymphatic filariasis in tropical countries. BIBLIOGRAPHIC REFERENCES: Ewert, A. and Emerson, G. 1975. Effects of diethylcarbamazine on third stage (infective) Brugia malayi larvae in cats. Amer. J. Trop. Med. Hyg. 24(1): 71-73 (previously reported as In Press). Bosworth, W. and Ewert, A. 1975. The effect of streptococcus on the persistence of Brugia malayi and on the production of elephantiasis in cats. Int'l. J. Parasitol. 5: In press.